Discounts for categories

Hello,

I would like to create discounts for category products. That sounds simple but it looks like it isn't. The discount system only allows you to select one category per discount. So I created a new discount and selected the next category but the system answers with an error message. I think that problem occurs because the categories have the same names. Is there a trick to set more than one category to one discount?

To get an idea about the problem see www.amocol.com/index.php/products-shop.html
We want to set a discount to all products who are listed as Resins.

Thank you for your help in advance.

Ok, I found out why I receive the message. When I do not enter a code it will fail for the next discount. So you need to enter a code to create multiply discounts.

The code field is a key value in the database discount table.